MELBOURNE — Japan and Australia signed the Mogami Memorandum aboard the JS Kumano frigate docked in Melbourne on April 18, 2026, committing Tokyo to supply up to 11 next-generation Mogami-class frigates to the Royal Australian Navy. The agreement is valued at up to A$20 billion (US$14.4 billion).

Japanese Defense Minister Shinjiro Koizumi and Australian Deputy Prime Minister Richard Marles jointly inaugurated what the two governments described as a north–south defense axis in the region. The first three vessels will be built by Mitsubishi Heavy Industries in Nagasaki to meet an accelerated delivery schedule by December 2029, while the remaining eight will be constructed in Henderson, Western Australia.

Japan's bid was selected over proposals from Germany's MEKO A-200, South Korea, and Spain. Australia favored the Japanese frigate proposal due to the maturity of its design, schedule reliability, and superior automation technology. The Mogami-class frigates can operate with a crew of 92, roughly half that of conventional frigates.

The Australian variant, called the Upgraded Mogami or New FFM, is equipped with 32 Mk 41 Vertical Launch System cells capable of carrying up to 128 Evolved Sea Sparrow Missiles, and is integrated with U.S. weapon systems such as the Naval Strike Missile and potentially Tomahawk cruise missiles. Australian Mogami-class units average around A$1.8 billion each, reflecting extensive technology transfer and the upgraded OYQ-1 combat management system. The fleet is intended to operate as part of an integrated combat system alongside U.S. and Japanese Aegis destroyers in high-intensity conflict scenarios in open waters.

The deal aims to align Australia with Japan in a de facto quasi-alliance and to balance China's military assertiveness in the Indo-Pacific. A previous Japanese bid for Australia's Soryu-class submarines, submitted approximately a decade before the 2026 signing, failed.

Under Prime Minister Sanae Takaichi, Japan relaxed its Three Principles on Transfer of Defense Equipment to enable the export of lethal systems to strategic partners, with Australia the primary beneficiary. Japan's defense export strategy involves deploying a common technological platform and calibrating capabilities to match each partner's risk profile and geopolitical role.

The two countries declared a Special Strategic Partnership in 2014. The Reciprocal Access Agreement, enacted in 2023 to streamline the deployment of troops and defense assets across each other's territories, represented Japan's first defense agreement with a country other than the United States since 1960. The Framework for Strategic Defence Coordination, launched in late 2025, encompasses intelligence-sharing and long-term defense policy alignment. Australia has also opened pathways for Japanese participation in AUKUS Pillar II, focusing on autonomous underwater systems, artificial intelligence, and quantum technologies.